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(No Model.) 2 Sheets-Sheet 1.

0. KELLNER. PROGESS 0F PRODUCING GELLULOSE No. 542,932. Patented July16, 1895.

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(No Model.) 2 Sheets-Sheet 2. 0. KELLNER.

PROCESS OF PRODUCING GELLULOSE.

Patented July 16, 1895.

NITED STATES PATENT rrrent PROCESS OF PRODUCING CELLULOSE.

SPECIFICATION forming part of Letters Patent No. 542,932, dated July 16,1895.

Application filed December 5, 1891. Serial No. 414,206. (No specimens.)Patented in England July 31, 1891, No. 12,970, and in Austria-HungaryDecember 8,1891,No.33,685 and No. 56,889-

To all whom it may concern.-

Be it known that I, CARL KELLNER, a subject of the Emperor ofAustria-Hungary, residing at Vienna, in the Province of Lower Austria,in the Empire of Austria-Hungary, have invented certain new and usefulImprovements in the Process of Producing Cellulose by Means of SulfurousAcid, (for which I have obtained Letters Patent in Austria-Hungary,dated December 8, 1891, No. 33,685 and No. 56,889, and in England, datedJuly 31, 1891, No. 12,970,) and I do hereby declare the following to bea full, clear, and exact description of the invention, such as willenable others skilled in the art to which it appertains to make and usethe same, reference being had to the accompanying drawings, and toletters of reference marked thereon, which form a part of thisspecification.

This invention relates to the manufacture of cellulose by the sulfiteprocess, and more especially to the treatment of the sulfite solutionprior to its introduction into the boiler or digester.

In the conversion of fibrous materials into cellulose by the sulfiteprocess the sulfite solution has prior to this my invention beenintroduced into the boiler or digester, together with the fibrousmaterial,in acold condition,

and then heated either directly by the injection of steam or indirectlyby means of a heater-coil in the digester or a heating-j acketencompassing the digester. This mode of heating the digester contentsfrom a normal to an operative temperature takes, as is well known,acomparatively long time, which may be considered as lost time, since nopractical function or operation takes place untilthe sulfite-liquor hasbeen heated to the required temperature. On the other hand, during thisoperation monosultite of calcium in considerable quantities is formed,due, no doubt, to the separation under action of heat of a portion ofthe lime-solvent-i. a, the sulfurous aoid-whereby a portion of the limeis set free.

' prevented during the heating of the sulfite solution from a normal tothe required tem- 5o perature at which there is a sufficient pressure inthe digester to prevent the separation of the sulfurous acid in the formof a gas. The formation of calcium monosulfite is not only detrimentalin that it forms a non-conductive crust upon the digester-walls if thedigester is heated externally or upon the surfaces of the heater-coilswhen the digester is heated internally, requiring a greater amount ofcaloric to heat the contents, while the monosulfite has a detrimentalaction upon the cellulose in that the latter becomes more or lessdiscolored, thereby increasing the labor and expense of bleaching.

' My invention has for its object to obviate these disadvantages byremoval of all or nearly all of the monosulfite that is usually formedin heating a charge of sulfite solution from a normal to the requiredeffective temperature before admitting the liquor to the digester, whichI efiect by heating the sulfite solution in a separate vessel to thedesired temperature, allowing the calcium monosulfite to subside, andthen transferring the hot solution to the digester containing thematerial to be converted into cellulose.

It is obvious that by means of this mode of procedure the solution inthe digester can be readily maintained at or raised to the desiredtemperature and 'a sufficient pressure estab lished within thedigesterto prevent the further separation of sulfurous acid from the sulfitesolution'and consequently a further formation of calcium monosulfite.

same as a solvent for the separated calcium monosulfite.

In the accompanying drawings I have illustrated heaters of simpleconstruction, by means of which the sulfite solution may be heatedbefore its introduction into the digester and the sulfurousacid gasesevolved during the heating recovered and utilized as a solvent for thecalcium monosulfite formed during such heating.

Figure l is a central vertical section of an upright heater withcondenser. Fig. 2 is a longitudinal central sectional elevation; andFig. 3, a transverse section of a horizontal heater, the condenser beingomitted.

Referring to Fig. 1, the uprightheater consists of a boiler a,containing a steam-coil b, to which steam is admitted through the valvedpipe 0, the water of condensation being collected in a suitable trap e,connected with theopposite terminal of the coil 1) through a valved pipe(1. At its upper end the heater has a manhole normally closed by a coverm, provided with a pressuregage, the heater having, also, a thermometert at its upper and lower ends, respectively. In the bottom of the heateris provided a valved purge-pipe n, so that the apparatus may be cleansedfrom time to time, the sulfite solution being introduced through valvedpi pe f and discharged through valved pipe g. At its upper end theheater is connected by a valved pipe h with one terminal of acondenser-coil j, the other terminal of the coil beingconnectcd bya pipe7" with a suitable receiver for the products of condensation.

The condenser 7c is composed of two concentric vessels, between whichthe condensercoil is arranged, the inner vessel having ports in itswalls at its lower end, through which inner vessel thedischarge-terminal of the coil is carried. The cooling agent is fed tothe inner vessel through pipe Z, thence passes through the ports intothe space between the said inner vessel and "the outer vessel and upthrough the overflow Z.

'lhesulfurous-acid gases a nd vapors evolved during the heating of thesulfite solution are condensed in the condenser 70, and thence flow to asuitable collector, which also collects all non-condensed gases, whichlatter, as well as the products of condensation, are pumped back orotherwise returned to the heater, when the same is again charged inorder to dissolve any calcium monosulfite formed during the heating ofthe previous charge of sulfite solution.

In order to facilitate the separation of the calcium monosulfite andalso to hold the same in suspension as much as possible during thepreheating of the solution, and thereby prevent its too rapiddeposition, I prefer to provide the heater with an agitator that willkeep the monosulfite in motion and prevent its deposition as far aspossible, as shown in Figs. 2 and 3. In these figures I have shown ahorizontal heater a inclosed within a pro tion between the coil and thetrap e. The sultite solution is introduced through a perforated pipep,connected with avalved inletpipe f, and s is what is termed an oil-bagforthe reception of athermometenn being the purge-pipe and g the valvedexhaust-pipe.

The operation may be briefly described as follows: The heater is chargedwith sulfite solution, which is heated, preferably, to a degree higherthan its boiling-point, the agitator being kept in motion to prevent thedeposition of the monosulfite formed by the decomposition or partialdecomposition of the sulfite solution under the action of heat. When thesolution has been heated to the desired temperature, the rotation ofthe. agitator is stopped and the calcium monosulfite separated from thesolution is allowed to subside, after which the hot solution istransferred to the digester or digesters previously charged with wood.The gases evolved during the heating ofthe sulfite solution, whichconsist, chiefly, of sulfurous acid, (80 are conducted to the condenser70, and from the latter to a suitable storage-vessel, to which are alsoconducted the gases evolved in the digesters and drawn olf after thereduction of the fibrous material. After the discharge of the hotsolution from the heater and before it is again charged with sulfitesolution the sulfurous acid from the storage-vessel is introduced intosaid heater for the purpose of dissolving the calcium monosulfiteseparated from the previously-heated sulfite solution, after which theheater is or may be again supplied with cold sulfite solution. In thismanner I provide against the separation of the calcium monosulfite fromsulfite solutions in the digesters, owing to the fact that the sulfitesolution is not heated therein from a normal temperature to theboiling-point, during which the monosulfite is chiefly formed, but saidsolution is supplied to the digester at that or even a highertemperature, so that a sufficient pressure can be maintained within thedigesters to prevent the formation of calcium monosulfite. On the otherhand, I also utilize the calcium monosulfite, together with thesulfurous-acid gases separated during the heating of the sulfitesolutions, by combining the same to form a sulfite solution.

Having thus described my invention, What I claim as new therein, anddesire to secure by Letters Patent, is-

1. In the manufacture of cellulose by the sulfite process, the mode ofpreventing the formation of monosulfite of calcium in the di gestersduring the heating of the sulfite solution from a normal to the requiredtemperature, which consists in heating the solution in a separatevessel, separating therefrom the monosulfite of calcium formed duringsuch heating, and introducing the hot solution into the digester,substantially as set forth.

2. In the manufacture of cellulose by the sulfite process, the mode ofpreventing the formation of monosulfite of calcium in the digestersduring the heating of. the sulfite solusame as a solvent for theseparated nionosul- I tion from a normalto the required temperafite,substantially as set forth. IO

ture, which consists in heating the solution In testimony whereof Iaffix my signature in a separate vessel, separating therefrom the inpresence of two Witnesses.

5 monosulfite of calcium formed during such CARL KELLNER.

heating, introducing the hot solution into the Witnesses: digester,collecting and condensing the sul- JULIUS GoLDscHMIDT,

' furous-acid gases evolved and utilizing the A. SGHLESSING.

